Integrated Fan-Out Package Structures with Recesses in Molding Compound

ABSTRACT

A package includes a first die and a second die. The first die includes a first substrate and a first metal pad overlying the first substrate. The second die includes a second substrate and a second metal pad overlying the second substrate. A molding compound molds the first die and the second die therein. The molding compound has a first portion between the first die and the second die, and a second portion, which may form a ring encircles the first portion. The first portion and the second portion are on opposite sides of the first die. The first portion has a first top surface. The second portion has a second top surface higher than the first top surface.

BACKGROUND

With the evolving of semiconductor technologies, semiconductorchips/dies are becoming increasingly smaller. In the meantime, morefunctions need to be integrated into the semiconductor dies.Accordingly, the semiconductor dies need to have increasingly greaternumbers of I/O pads packed into smaller areas, and the density of theI/O pads rises quickly with time. As a result, the packaging of thesemiconductor dies becomes more difficult, which adversely affects theyield of the packaging.

Conventional package technologies can be divided into two categories. Inthe first category, dies on a wafer are packaged before they are sawed.This packaging technology has some advantageous features, such as agreater throughput and a lower cost. Further, less underfill or moldingcompound is needed. However, this packaging technology also suffers fromdrawbacks. As aforementioned, the sizes of the dies are becomingincreasingly smaller, and the respective packages can only be fan-intype packages, in which the I/O pads of each die are limited to a regiondirectly over the surface of the respective die. With the limited areasof the dies, the number of the I/O pads is limited due to the limitationof the pitch of the I/O pads. If the pitch of the pads is to bedecreased, solder bridges may occur. Additionally, under the fixedball-size requirement, solder balls must have a certain size, which inturn limits the number of solder balls that can be packed on the surfaceof a die.

In the other category of packaging, dies are sawed from wafers beforethey are packaged, and only “known-good-dies” are packaged. Anadvantageous feature of this packaging technology is the possibility offorming fan-out packages, which means the I/O pads on a die can beredistributed to a greater area than the die, and hence the number ofI/O pads packed on the surfaces of the dies can be increased.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the embodiments, and the advantagesthereof, reference is now made to the following descriptions taken inconjunction with the accompanying drawings, in which:

FIGS. 1 through 12A are cross-sectional views of intermediate stages inthe manufacturing of an Integrated Fan-Out (InFO) package in accordancewith some exemplary embodiments; and

FIG. 12B illustrates a top view of an InFO package in accordance withexemplary embodiments.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

The making and using of the embodiments of the disclosure are discussedin detail below. It should be appreciated, however, that the embodimentsprovide many applicable concepts that can be embodied in a wide varietyof specific contexts. The specific embodiments discussed areillustrative, and do not limit the scope of the disclosure.

An Integrated Fan-Out (InFO) package including fan-out redistributionlines and the methods of forming the same are provided in accordancewith various exemplary embodiments. The intermediate stages of formingthe InFO package are illustrated. The variations of the embodiments arediscussed. Throughout the various views and illustrative embodiments,like reference numbers are used to designate like elements.

FIGS. 1 through 12A are cross-sectional views of intermediate stages inthe manufacturing of a package structure in accordance with someexemplary embodiments. Referring to FIG. 1, carrier 20 is provided, andpolymer base layer 22 is laminated on carrier 20. Carrier 20 may be ablank glass carrier, a blank ceramic carrier, or the like. Polymer baselayer 22 may be formed of Ajinomoto Buildup Film (ABF), polyimide,PolyBenzOxazole (PBO), BenzoCycloButene (BCB), Solder Resist (SR) film,Die-Attach Film (DAF), or the like, although other types of polymers maybe used. Polymer base layer 22 has a planar top surface.

FIG. 2 illustrates the placement of device dies 100 and 200 over polymerbase layer 22. In some embodiments, an additional adhesive layer (notshown) is disposed underlying each of device dies 100 and 200 to adherethe respective device dies 100 and 200 to polymer base layer 22. Inalternative embodiments, no additional adhesive layer is disposed, anddevice dies 100 and 200 are in contact polymer base layer 22. Devicedies 100 and 200 may be logic device dies including logic transistorstherein. In some exemplary embodiments, device dies 100 and 200 aredesigned for mobile applications, and may include Central Computing Unit(CPU) dies, Power Management Integrated Circuit (PMIC) dies, Transceiver(TRX) dies, or the like. Device dies 100 and 200 may have structuresthat are different from each other, or may have structures identical toeach other. Each of device dies 100 and 200 includes a semiconductorsubstrate 120/220 (refer to FIG. 12A) that contacts the adhesive layer,wherein the back surface of the semiconductor substrate 120/220 is incontact with the adhesive layer. Semiconductor substrate 120 and 220 maybe silicon substrates in some embodiments. In some embodiments, eachdevice dies 100 and one of the neighboring device dies 200 are locatedclose each other, for example, with distance D1 being smaller than about150 μm. Distance D1 may also be greater than about 25 μm.

Device dies 100 and 200 are schematically illustrated in FIG. 2. FIG. 3illustrates a cross-sectional view of device die 100, wherein moredetails are illustrated. As shown in FIG. 3, device die 100 includessemiconductor substrate 120. Semiconductor substrate 120 may be a bulksilicon substrate or a silicon-on-insulator substrate, while othersemiconductor materials including group III, group IV, and group Velements may also be used. Integrated circuit devices such astransistors (schematically illustrated as 121) are formed at a surfaceof semiconductor substrate 120.

Device die 100 may further include Inter-Layer Dielectric (ILD) 122 oversemiconductor substrate 120, and metal layers 124 over ILD 122. Metallines 126 and vias 128 are formed in dielectric layers 125. Thecombination of metal lines at a same level is referred to a metal layerhereinafter. Accordingly, a plurality of metal layers 124 areinterconnected through vias 128. In some embodiments, dielectric layers125 are formed of low-k dielectric materials. The dielectric constants(k values) of the low-k dielectric materials may be less than about 3.0,or less than about 2.5, for example. Metal lines 126 and vias 128 may beformed of copper or copper alloys, although they can also be formed ofother metals.

Device dies 200 (FIG. 2) may have a structure similar to that of devicedie 100, although the structures of device dies 100 and 200 may also bedifferent from each other. Therefore, the materials and the structuresof the features in device dies 200 may be found referring to the likefeatures in device die 100 as described referring to FIG. 3. The likefeatures in device dies 200 are marked with reference numerals startingwith number “2,” which features correspond to the features in devicedies 100 and having reference numerals starting with number “1.” Some ofthe features in device die 200 are schematically illustrated in FIGS. 7and 12A.

Referring again to FIG. 3, metal pad 130 is formed over metal layers124, and may be electrically coupled to metal lines 126 and vias 128.Metal pad 130 may be an aluminum pad or an aluminum-copper pad, andhence is alternatively referred to as aluminum pad 130 hereinafter,although other metallic materials may be used. Passivation layer 132 isformed over metal layers 124. Portions of passivation layer 132 maycover the edge portions of aluminum pad 130. The central portion ofaluminum pad 130 is exposed through the opening in passivation layer132. Passivation layer 132 may be a single layer or a composite layer,and may be formed of a non-porous material. In some embodiments,passivation layer 132 is a composite layer comprising a silicon oxidelayer (not shown), and a silicon nitride layer (not shown) over thesilicon oxide layer. Alternatively, passivation layer 132 is formed ofUn-doped Silicate Glass (USG), silicon oxynitride, and/or the like.Throughout the description, top surface 132A of passivation layer 132 isreferred to as the top surface of device die 100 hereinafter.

Over passivation layer 132 and metal pad 130 resides protection film134. In some embodiments, protection film 134 comprises a BacksideGrinding (BG) tape, a laminating tape including a polyimide and anadhesive, an Ultra-Violet (UV) tape, or the like. Protection film 134may be the same film that is used in the manufacturing of device die100. For example, in the formation of device die 100, after theformation of passivation layer 132, a backside grinding tape is adheredto passivation layer 132, so that the backside of substrate 120 isgrinded in order to thin die 100 and the respective wafer. After thegrinding, the respective wafer is sawed together with the backsidegrinding tape to separate die 100 from other dies. A piece of backsidegrinding tape is left adhered to passivation layer 132, and becomesprotection film 134.

Referring to FIG. 4, molding material 42 is molded on device dies 100and 200. Molding material 42 fills the gaps between device dies 100 and200, and may be in contact with polymer base layer 22. Molding material42 may include a molding compound, a molding underfill, an epoxy, or aresin. The top surface of molding material 42 is higher than the topsurfaces of protection films 134 and 234, which cover device dies 100and 200, respectively.

Next, a grinding step is performed to remove excess portions of moldingmaterial 42, until protection films 134 and 234 are exposed. Theresulting structure is shown in FIG. 5. Molding material 42 includes aportion 42A between device die 100 and 200, and portions 42B surroundingportion 42A and device dies 100 and 200 (also refer to FIG. 12B).Molding material portion 42A has a top surface substantially level withthe top surfaces of protection films 134 and 234. Accordingly, moldingmaterial portion 42A includes a top portion 42′ above the top surface132A of device die 100 and/or top surface 232A of device die 200.Thickness T1 of the top portion 42′ of molding material portion 42A maybe in the range between about 3 μm and about 40 μm, for example. Afterthe grinding, molding material 42 has height H1, which may be greaterthan about 80 μm, and may be in the range between about 80 μm and about280 μm.

FIG. 6 illustrates the recessing of molding material portions 42A. Insome embodiments, the recessing is performed through laser drill, asschematically illustrated. The surrounding portions 42B are notrecessed. Accordingly, top surface 42A1 of the remaining moldingmaterial portion 42A is lower than top surface 42B1 of the surroundingportions 42B.

FIG. 7 illustrates a magnified view of device dies 100 and 200 andmolding material 42. As shown in FIG. 7, after the recessing, topsurface 42A1 of molding material portion 42A may be level with topsurfaces 132A of device die 100 and/or top surface 232A of device die200. In alternative embodiments, top surface 42A1 is higher than topsurfaces 132A and/or 232A. In yet alternative embodiments, top surface42A1 is lower than top surfaces 132A and/or 232A. As illustrated, topsurfaces 42A1 may also be lower than the bottom surfaces of metal pads130 and/or 230. Dashed lines 43 illustrate several possible positions oftop surfaces 42A1 in various embodiments. Alternatively stated, theremaining molding material portion 42A has height H3, wherein height H3may be greater than, equal to, or smaller than the height H2(thicknesses) of device die 100 and height H2′ of device die 200. Insome embodiments, height difference (H1-H3) is between about 2 μm andabout 35 μm. Height H3 may be greater than about 50 μm in some exemplaryembodiments.

Protection films 134 and 234 are then removed, as shown in FIG. 8.Passivation layers 132 and 232 (refer to FIG. 7) and metal pads 130 and230 are exposed. It is appreciated that if molding material portion 42Ais not recessed, the protruding portions of molding material portion42A, as illustrated by dashed lines 45, will form humps that protrudeabove the top surfaces of dies 100 and 200, which are on the oppositesides of molding material portion 42A.

The humps may have the heights equal to the thicknesses of protectionfilms 134 and 234. Accordingly, the heights of the humps may be in therange between about 3 μm and about 40 μm. The humps thus form long andtall walls that have the length equal to the length of device dies 100and 200. Hence, if the humps are left un-removed, the humps will affectthe subsequent photolithography processes, and may cause cracks in theresulting package.

Next, referring to FIG. 9, Redistribution Lines (RDLs) 44 are formedover molding material 42 to connect to metal pads 130 and 230. RDLs 44may also interconnect metal pads 130 and 230. In accordance with variousembodiments, one or a plurality of dielectric layers 46 are formed overthe structure shown in FIG. 8, with RDLs 44 formed in dielectric layers46. FIG. 9 illustrates the schematic view of RDLs 44 and dielectriclayers 46, while the details of RDLs 44 and dielectric layers 46 may befound in FIG. 12A. In some exemplary formation process, the formation ofone layer of RDLs 44 and dielectric layers 46 includes forming a blanketcopper seed layer, forming and patterning a mask layer over the blanketcopper seed layer, performing a plating to form RDLs 44, removing themask layer, and performing a flash etching to remove the portions of theblanket copper seed layer not covered by RDLs 44. RDLs 44 may comprise ametal or a metal alloy including aluminum, copper, tungsten, nickel,and/or alloys thereof.

FIG. 12A illustrates a more detailed view of RDLs 44 and dielectriclayers 46. In FIG. 12, two layers of RDLs 44 (including 44A and 44B) areillustrated. Dielectric layers 46 (including 46A and 46B) in theseembodiments may comprise polyimide, benzocyclobutene (BCB),polybenzoxazole (PBO), or the like. Alternatively, dielectric layers 46may include non-organic dielectric materials such as silicon oxide,silicon nitride, silicon carbide, silicon oxynitride, or the like.

FIG. 10 illustrates the formation of electrical connectors 48 inaccordance with some exemplary embodiments. The formation of electricalconnectors 48 may include forming Under-Bump Metallurgies (UBMs) 47 onRDLs 44, placing solder balls on the exposed portions of UBMs 47, andthen reflowing the solder balls. In alternative embodiments, theformation of electrical connectors 48 includes performing a plating stepto form solder regions over RDLs 44 or UBMs 47, and then reflowing thesolder regions. Electrical connectors 48 may also include metal pillars,or metal pillars and solder caps, which may also be formed throughplating. In the embodiments in which electrical connectors 48 are solderballs, the lower parts of solder balls 48 may be molded in moldingcompound 54, while the upper parts of solder balls 48 are exposed.Throughout the description, the combined structure including device dies100 and 200, molding material 42, and the overlying RDLs 44 anddielectric layers 46 is referred to as package 50, which may be acomposite wafer.

Next, package 50 is de-bonded from carrier 20. Polymer base layer 22 andadhesive layers (if any) are also removed from package 50. The resultingstructure is shown in FIG. 11. In alternative embodiments, polymer baselayer 22 is not removed, and is left in the resulting package. As aresult of the de-bonding, molding material 42 and the back surfaces ofdevice dies 100 and 200 are exposed. Nest, package 50 is further adheredto dicing tape 52, wherein electrical connectors 48 face toward, and maycontact, dicing tape 52.

Next, package 50 is sawed into a plurality of packages 60. FIGS. 12A and12B illustrate a cross-sectional view and a top view, respectively, ofone of packages 60. As shown in FIG. 12A, one or more dielectric layers46 (including 46A and 46B), which may be polymer layers, are overpassivation layers 132 and 232, and continuously extends from the regiondirectly over device die 100 to the region directly over device die 200.Dielectric layers 46 may be polymer layers comprising polyimide, PBO,BCB, or the like. RDLs 44 may include one or more layers such as RDLs44A and RDLs 44B, which are formed in dielectric layers 46. The topsurface 42A1 of molding material portion 42A is in contact with thebottom surface of dielectric layer 46A. The top surface 42A1 of moldingmaterial portion 42A is lower than top surface 42B1 of portions 42B ofmolding material 42, which portions 42B form a ring surrounding bothdevice dies 100 and 200.

As shown in FIG. 12B, portions 42A and 42B of molding material 42 areillustrated. Portion 42B forms a ring encircling portion 42A and devicedies 100 and 200. Furthermore, the opposite ends of molding materialportion 42A are connected to ring portion 42B to form a continuousmolding material.

In the embodiments of the present disclosure, by recessing the portionof molding compound between closely located device dies in the samepackage, the humps of molding materials are removed. The processdifficulty (such as to the subsequent lithography process) caused by thehumps and the package crack caused by the humps are eliminated.

In accordance with some embodiments, a package includes a first die anda second die. The first die includes a first substrate and a first metalpad overlying the first substrate. The second die includes a secondsubstrate and a second metal pad overlying the second substrate. Amolding compound molds the first die and the second die therein. Themolding compound has a first portion between the first die and thesecond die, and a second portion, which may form a ring encircles thefirst portion. The first portion and the second portion are on oppositesides of the first die. The first portion has a first top surface. Thesecond portion has a second top surface higher than the first topsurface.

In accordance with other embodiments, a package includes a first die anda second die. The first die includes a first substrate, a first metalpad over the first substrate, and a first passivation layer coveringedge portions of the first metal pad, with a center portion of the firstmetal pad un-covered by the first passivation layer. The firstpassivation layer has a first top surface. The second die includes asecond substrate, a second metal pad over the second substrate, and asecond passivation layer covering edge portions of the second metal pad,with a center portion of the second metal pad un-covered by the secondpassivation layer. The second passivation layer comprises a second topsurface. A molding compound molds the first die and the second dietherein. The molding compound includes a first portion between the firstdie and the second die, wherein the first portion comprises a third topsurface, and a second portion forming a ring surrounding the firstportion of the molding compound, the first die, and the second die. Thesecond portion has a second top surface higher than the first topsurface.

In accordance with yet other embodiments, a method includes placing afirst die and a second die over a carrier, wherein the first dieincludes a first substrate and a first metal pad over the firstsubstrate, and the second die includes a second substrate and a secondmetal pad over the second substrate. The method further includes moldingthe first die and the second die in a molding compound, and grinding themolding compound. After the grinding, a first portion of the moldingcompound is recessed, wherein the first portion is between the first dieand the second die, and wherein a second portion of the molding compoundis not recessed. Redistribution lines are then formed over andelectrically coupled to the first metal pad and the second metal pad.

Although the embodiments and their advantages have been described indetail, it should be understood that various changes, substitutions andalterations can be made herein without departing from the spirit andscope of the embodiments as defined by the appended claims. Moreover,the scope of the present application is not intended to be limited tothe particular embodiments of the process, machine, manufacture, andcomposition of matter, means, methods and steps described in thespecification. As one of ordinary skill in the art will readilyappreciate from the disclosure, processes, machines, manufacture,compositions of matter, means, methods, or steps, presently existing orlater to be developed, that perform substantially the same function orachieve substantially the same result as the corresponding embodimentsdescribed herein may be utilized according to the disclosure.Accordingly, the appended claims are intended to include within theirscope such processes, machines, manufacture, compositions of matter,means, methods, or steps. In addition, each claim constitutes a separateembodiment, and the combination of various claims and embodiments arewithin the scope of the disclosure.

What is claimed is:
 1. A package comprising: a first die comprising afirst substrate and a first metal pad overlying the first substrate; asecond die comprising a second substrate; and a molding compound moldingthe first die and the second die therein, wherein the molding compoundcomprises: a first portion between the first die and the second die,wherein the first portion comprises a first top surface; and a secondportion, wherein the first portion and the second portion are onopposite sides of the first die, and wherein the second portion has asecond top surface higher than the first top surface.
 2. The package ofclaim 1, wherein the second portion of the molding compound is comprisedin a ring portion of the molding compound, wherein the ring portionencircles the first portion of the molding compound, the first die, andthe second die, and wherein all top surface of the ring portion iscoplanar with the second top surface.
 3. The package of claim 1, whereina height different between the first top surface and the second topsurface is between about 2 μm and about 35 μm.
 4. The package of claim1, wherein the first die further comprises: a passivation layer coveringedge portions of the first metal pad, with a center portion of the firstmetal pad un-covered by the passivation layer, wherein the first topsurface is substantially level with a top surface of the passivationlayer.
 5. The package of claim 1, wherein the first die furthercomprises: a passivation layer covering edge portions of the first metalpad, with a center portion of the first metal pad un-covered by thepassivation layer, wherein the first top surface is higher than a topsurface of the passivation layer.
 6. The package of claim 1, wherein thefirst die further comprises: a passivation layer covering edge portionsof the first metal pad, with a center portion of the first metal padun-covered by the passivation layer, wherein the first top surface islower than a top surface of the passivation layer.
 7. The package ofclaim 1 further comprising: a polymer layer continuously extending froma region overlapping the first die into a region overlapping the seconddie, wherein the first top surface is in contact with a bottom surfaceof the polymer layer; a first redistribution line penetrating throughthe polymer layer to electrically couple to the first metal pad; asecond metal pad in the second die and over the second substrate; and asecond redistribution line penetrating through the polymer layer toelectrically couple to the second metal pad.
 8. A package comprising: afirst die comprising: a first substrate; a first metal pad over thefirst substrate; and a first passivation layer covering edge portions ofthe first metal pad, with a center portion of the first metal padun-covered by the first passivation layer, wherein the first passivationlayer comprises a first top surface; a second die comprising: a secondsubstrate; a second metal pad over the second substrate; and a secondpassivation layer covering edge portions of the second metal pad, with acenter portion of the second metal pad un-covered by the secondpassivation layer, wherein the second passivation layer comprises asecond top surface; a molding compound molding the first die and thesecond die therein, wherein the molding compound comprises: a firstportion between the first die and the second die, wherein the firstportion comprises a third top surface; and a second portion forming aring surrounding the first portion of the molding compound, the firstdie, and the second die, wherein the second portion has a fourth topsurface higher than the third top surface.
 9. The package of claim 8,wherein two opposite ends of the first portion of the molding compoundare continuously connected to the second portion of the moldingcompound, and wherein the first portion and the second portion areformed of as a same material.
 10. The package of claim 8, wherein thethird top surface is level with or lower than one of the first topsurface and the second top surface.
 11. The package of claim 8 furthercomprising: a polymer layer continuously extending from a regionoverlapping the first die into a region overlapping the second die,wherein the third top surface is in contact with a bottom surface of thepolymer layer; a first redistribution line penetrating through thepolymer layer to electrically couple to the first metal pad; and asecond redistribution line penetrating through the polymer layer toelectrically couple to the second metal pad.
 12. The package of claim11, wherein the first top surface and the second top surface are incontact with the bottom surface of the polymer layer.
 13. The package ofclaim 8, wherein the first die and the second die have differentstructures.
 14. The package of claim 8, wherein the fourth top surfaceis higher than the third top surface by a difference between about 2 μmand about 35 μm.
 15. A method comprising: placing a first die over acarrier, wherein the first die comprises a first substrate and a firstmetal pad over the first substrate; placing a second die over thecarrier, wherein the second die comprises a second substrate and asecond metal pad over the second substrate; molding the first die andthe second die in a molding compound; grinding the molding compound;after the grinding, recessing a first portion of the molding compound,wherein the first portion is between the first die and the second die,and wherein a second portion of the molding compound is not recessed;and forming redistribution lines over and electrically coupled to thefirst metal pad and the second metal pad.
 16. The method of claim 15,wherein the recessing is performed through laser drilling.
 17. Themethod of claim 15, wherein after the recessing, a bottom portion of thefirst portion of the molding compound is left un-removed.
 18. The methodof claim 15, wherein the first die and the second die are covered by afirst protection film and a second protection film, respectively,wherein the grinding is stopped when the first protection film and thesecond protection film are exposed, and wherein the method furthercomprises: after the grinding, removing the first protection film and asecond protection film to expose the first die and the second die,respectively, wherein the first metal pad and the second metal pad areexposed after the removing.
 19. The method of claim 15 furthercomprising: after forming the redistribution lines, forming electricalconnectors over and electrically coupled to the redistribution lines;and performing a die saw to form a package comprising the first die, thesecond die, and the first and the second portions of the moldingcompound.
 20. The method of claim 15 further comprising de-bonding thefirst die, the second die, and the molding compound from the carrier.